1997 Johnson Evinrude "EU" 9.9 thru 30 2-Cylinder Service Manual, P/N 507263, Page 294Get this manual
Battery Cable Extension The following are MINIMUM specifications for stranded copper cable without splicesCable measurements given are from the motor to the batteryThe maximum length is 20 feet, regardless of cable diameterINotel These specifications do not apply to aluminum battery cablesCNC does not recommend the use of aluminum battery cables